Stock-Based Compensation (Summary Of SAR Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Stock Appreciation Rights [Roll Forward]
Outstanding, Shares	1,024,922	1,179,286
Granted, Shares	168,716
Forfeited, Shares	(13,884)
Expired, Shares	(516)
Exercised, Shares	(308,680)
Outstanding, Weighted Average Exercise Price, Beginning Balance	$ 37.13
Granted, Weighted Average Exercise Price	58.42
Forfeited, Weighted Average Exercise Price	48.09
Expired, Weighted Average Exercise Price	44.16
Exercised, Weighted Average Exercise Price	31.35
Outstanding, Weighted Average Exercise Price, Ending Balance	$ 42.23
Outstanding, Weighted Average Remaining Contractual Term (in years)	7 years
Outstanding, Aggregate Intrinsic Value, Ending Balance	$ 24,387